"Calligraphy" is the art of fine writing. Nowadays in various countries throughout the world, writing for practical purposes is done using pencil or pen, though brush and ink calligraphy is still widely practiced as a separate art. In the Western culture, calligraphy is typically performed using a rigid broad edged pen. An Old English style print is one of the most commonly used styles of Western calligraphy. In this style, stroke width of a character varies usually at the ends of a linear stroke and/or along a portion of a curved stroke. This is accomplished by stroke width being a function of the direction in which the pen is travelling, the angle at which the nib (rigid broad edge) is held with respect to a horizontal axis on the writing surface, and to some degree, force applied to the pen. Some characters require a turning or twisting of the pen between the fingers to vary stroke width in appropriate positions.
In Asian cultures, particularly in China and Japan, calligraphy is typically performed using a simple brush formed of a handle and bristles attached to one end of the handle. Chinese or Japanese calligraphy is called Kanji. Each Kanji character is comprised of a number of strokes where the ordering of the strokes and their form is strictly defined by the type of script to which the character belongs. Some characters are so complicated that they are comprised of more than 30 strokes.
Most, if not all, calligraphy is still performed by brush and ink as described above. One of the problems of inputting calligraphy into a computer system, and more generally of data processing in Asian cultures, is the difficulty in entering Asian calligraphy through a keyboard. Generally in data processing in Asian cultures, a single character is broken down into its constituent strokes and each stroke corresponds to a key on a typical keyboard. Depending on the complexity of the character there can be few or many keystrokes needed to enter a single character. The complexity of an average Kanji character and the thousands of characters in the language make inputting data for a form, for example, an extremely difficult task for someone who is not an expert Kanji typist. Hence, there is a need for a less complicated method for inputting Kanji (calligraphy) characters into a computer system.
Inputting devices other than the keyboard have been considered but with little to no advantage. Kanji characters made with a ball point pen or other non-force-sensitive writing implement lack proper visual feedback. C.G. Leedham and A.C. Downton in "On-line Recognition of Pittman's Handwritten Shorthand - an Evolution of Potential", International Journal of Man-Machine Studies, Volume 24, Pages 375-393 (1986) showed that the lack of proper visual feedback affects writing dynamics and changes writing style, as well as the process of stroke creation. Using a ball point pen to create a syntactically correct, force sensitive Kanji stroke would require the writer to scribble over sections of the stroke in order to show variability in stroke thickness. Of course, force sensing is not enough to provide perfectly realistic visual feedback, but it aids in providing visual feedback closer to what the writer expects.
Most "brushes" in computer-based paint systems are incapable of giving realistic brush stroke feedback dependent on force applied to the brush, size and shape of the brush, and speed of brush stroke. In addition, most "brushes" in computer based paint systems use a single static drawing primitive repeatedly drawn as a function of the movement of the input device. In some systems such as FullPaint (from Ann Arbor Softwares, Inc.) and SuperPaint (Copyright 1986, Bill Snyder) available for the MacIntosh of Apple Computer, Inc., as the input device, the mouse, moves from point A to point B, the entire path joining the two points is filled with "paint". The user can not dynamically change drawing primitives during the creation of a stroke, except by going to a menu and choosing a submenu for brush shape and/or size. In other computer based paint systems, the single primitive itself is drawn at each sample point, giving a non-continuous series of dots or filled circles, or whatever geometric shape the drawing primitive happens to be.
Further, computer based paint systems that use a 2-D mouse as their input device are not capable of expressing stroke width as a function of force. For applications that require the input device to be sensitive to force, these computer based paint systems do not work well. Steve Strassman in "Hairy Brushes", SIGGRAPH Proceedings 1986, Volume 20, No. 4, Pages 225-232, modelled a non-real-time brush as a compound object composed of bristles, and kept track of the physical state of the brush and remaining amount of ink over the course of the stroke. Strassman's "stroke" is described as a path whose constituting control points each have a force value associated with them. The force value for each control point is input by the user through the keyboard.
Accordingly there is a need for a computer based system for brush writing (i.e. calligraphy).